Operant training techniques are used to establish behavioral measures for noxious and non-noxious thermal stimuli presented to the upper lip of the rhesus monkey. The primary paradigm for studying supra-threshold warming stimuli has been a reaction time measure. Currently, the project has been expanded to describe the behavioral effects of both intensity and rate of stimulation by using the fastest reaction time method. Additionally, monkeys are being shaped to respond to the termination of a non-noxious warming stimulus so that subsequent escape behavior elicited by noxious stmuli can be used to infer "pain". These awake responding animals, once electrically implanted will provide correlative behavioral and electrophysiological information. Concurrent human reaction time studies have manipulated three stimulus parameters: intensity, rate of change and adapting temperature.